Bradi Baker has been marching for a cause since 1968, when her mother took her along on the famous Poor People's Campaign march on Washington commemorating slain civil rights leader Martin Luther lKing Jr.

Last week, Baker, who lives in Arlington, began another hike -- 736 miles from Copenhagen to Paris as part of an international group protesting the spread of nuclear arms.

During the 45-day hike, she hopes to average 15 to 20 miles a day in her effort to spark support for nuclear disarmament. Along the route, she and other hikers will try to encourage local people to march for part of the way. An estimated 2,000 people joined the hike on the first day. Baker estimated that 75 people would finish.

Baker, 22, first heard about the European walk at a potluck supper in Arlington last month where the Norwegian coordinator for the march was a guest.

Although Baker was interested in the march, she wasn't sure how to answer when the coordinator asked, "Why don't you join us?"

The major stumbling block for Baker was the $600 airfare she needed to get to Denmark.

"I have never been abroad," Baker said, "and figured that I would to to Africa before anywhere else. Yet I had a reason and a cause to go to Europe."

After talking with friends, she launched a door-to-door fundraising campaign in Arlington and Washington. For 50 cents each, she sold pamphlets, donated to her by Women's Strike for Peace, a Washington-based anti-nuclear lobbying group.

"My parents were embarrassed," said Baker, who graduated in June, 1980, from the University of Minnesota and moved to Arlington in February after working as paralegal and a hoslpital ward secretary in Chicago.

Baker's parents live in Evanston, Ill.

"They asked me, 'Why do you have to raise money that way? Why do you have to walk in this march?" Like so many people, my mother feels that there's nothing she can do about nuclear power. But I say, 'well, this is a small step but it's the best I can do.'"

That wasn't the only opposition Baker encountered.

On her first day raising funds, she was waiting for a bus to take her from Arlington to Washington when she saw a woman trimming a hedge.

"I went over to her and explained my plan. And then she asked me if I loved my country?

"I said, 'Yes. America's a great country.'

"Then she looked at me and she said, 'You know, the Soviets aren't going to drop the bomb on our country. They're too smart. They're going to infiltrate our country with people like you.'"

Although that first encounter was discouraging, Baker found during her week-long campaign that people generally were friendly and supported her plans.

One person, she recalls, told her "You know, we need more people like you."

Baker made $200 in her door-to-door campaign. From contacts she made along the way, she was introduced to organizations, churches and private individuals who donated the remaining $400.

Five years ago, Baker joined the Continental Walk of 1976, organized in part by the Community for Creative Non-Violence, a Washington-based activist group and one of her sponsors for the European walk. Although the Continental Walk started in California in January, 1976, and ended in Washington in October, Baker joined the march in Illinois, where she organized a local group to meet the main body of 50 hikers.

The 1976 march taught Baker some of the determination that helped her in her fundraising and which she expects to again help her in the march through Europe.

"Your feet get blisters on them. And some days you just don't feel like walking," said Baker. "But you just keep on." CAPTION:

Picture, Antinuclear marcher Bradi Baker demonstrates her stride. By James Thresher -- The Washington Post